Hi, If the resistors were in the load circuit when the output blew they will probably be around 1 OHM wire wound. Hamrad should have some 5w devices. if it works, great. it the power is low, these may need to be anything as low as 0.1 Ohm.

Hi, Sorry that never fixed the problem. The next lot to look at are output and driver bias resistors which could burn up in some circumstances.
The values as a rule of thumb will be from 100 ohms up to no more that say 470 at the upper limit. It is not likely that anything higher than that will burn quickly.
I would try 220 ohm half watts and watch carefully when you switch on. Have you checked out your driver transistors? I would........Now!
Its difficult to say with certainty because you can incur distortion etc if you mess too much but give it a try!